Under the term "abrasive surface" in the sense of the invention is meant a chip-removing surface of the tool, which does not have uniformly directed cutting edges or the like. This includes all tools with a granular working surface, for example grinding tools, however, also tools for electrolytic or electro-erosive or electrochemical material removal. (This does not include for example shaving gears.)
A known apparatus works in such a manner that only one side of the tool teeth engages the counterflank of the workpiece teeth. A backlash exists on the other tooth side. During a working operation, it is possible to change the effective tooth side. The guide gears can run without clearance. It can be preferable--in particular if the tool is moved toward the workpiece by a change in the center-distance--if the guide gears also engage one another on one tooth side, namely, referred to the tool-workpiece pairing with the other tooth side. Then both the workpiece-tool pairing and also the guide gear pairing run with backlash, however, the entire gearing runs without clearance (i.e. no play). The known apparatus works practically without longitudinal feed (German Pat. No. 33 04 980.7).
In the known apparatus of this type, the tooth flanks were pressed onto one another with the help of a braking mechanism and/or with the help of flywheel masses. The working flanks were changed either through a change in the direction of rotation of the drive motor and/or by means of clutches.
The basic purpose of the invention is to simplify and also possibly accelerate the exchange of the working flanks, and to more simply regulate the pressure of the tooth flanks which act on one another.
The basic purpose of the invention is attained by providing an apparatus of the above-described type, and which a control gear for causing an existing rotation to undergo an additional amount of rotation. Such a control gear can for example be a so-called total gearing (planetary gearing) with two center gears and a planetary web. (Such gears are known). Two of the mentioned members then facilitate the normal drive or output and the third member facilitates the additional amount of rotation.
If the additional rotation is only limited, then a simplification is possible by the use of helically toothed gears, of which one is longitudinally movable and drivable therefor. The longitudinal movement causes then the additional rotation at the output of the control gear.
Further advantages and characteristics of the invention result from the following description.